Conventionally, a polyimide has been widely used in the fields of molding materials, composite materials, electrical and electronic parts since a polyimide has excellent heat resistance and also has excellent properties in terms of mechanical physical properties, chemical resistance, flame retardancy and electrical characteristics. Recently, developments of microelectronics technologies are remarkable in the field of electrical and electronic parts. In particular, large computers employ a multilayer circuit board so that high-speed signal transmission is necessary to the large computers. However, when the dielectric constant of a board material is large, a delay in signal transmission occurs, which hinders speed-up. A polyimide is used for an interlayer insulation film of a multilayer wiring structure. However, from these reasons, a decrease in dielectric constant is further required of a polyimide in addition to its conventional excellent insulation properties.
On the other hand, in order to secure insulation reliability and dimensional stability, which are essential for high-density packaging accompanied by the recent progress of electronic materials, a resin for electronic materials is required to exhibit low dielectric characteristics even in high-humidity environment. However, generally, the dielectric characteristics of a polyimide at a moisture-absorbed time largely differ from those at a dried time since an imide group is apt to absorb moisture. This is a problem with regard to the employment of a polyimide as electronic materials.
A variety of polyimides and polyamic acids, which are raw materials for polyimides, have been proposed for solving these problems (for instance, JP-A-10-152559). However, these proposals are not sufficient for coping with the recent demand for further high-performance in the electronic material field.